Schiff Base Complexes with Covalently Anchored Luminophores: Self-Enhanced Electrochemiluminescence Detection of Neomycin

A novel electrochemiluminescence (ECL) amplification strategy was established aiming to overcome the inherent shortcomings of the current oxygen (O2) coreactant ECL systems. Macrocyclic Schiff base Fe complexes were rationally designed as a novel integrated ECL emitter by iminium linkage between N-(4-aminobutyl)-N-ethylisoluminol (ABEI) and 1,10-phenanthroline-2,9-dicarbaldehyde (PDL) and postmetalation of the macrocyclic Schiff base. Covalently combining luminophore ABEI with a catalytic center endowed the novel ECL emitter with both remarkable redox electrocatalytic properties and significantly enhanced ECL efficiency. The high content of ferrous iron and the dominantly active low-spin Fe state greatly contributed to the inherent catalytic activity for O2 activation. The rational modification of luminophore optimized the spatial distribution and simultaneously shortened the species transport distance of coreactant radicals generated in situ from dissolved O2, resulting in significantly self-enhanced ECL efficiency. Neomycin, which posed a growing threat to aquatic biodiversity and environmental safety, as the model antibiotic was successfully detected with a detection limit of 0.21 pM (S/N = 3), clarifying a promising application prospect of this new luminophore-embedded ECL amplification strategy in biological analysis and environmental monitoring.